This invention relates to a durable and imaged flame-retardant nonwoven fabric that can be used for flame-retardant apparel and other related applications. There are numerous flame-retardant fibers commercially available. E. I du Pont de Nemours and Company provides flame-retardant aramid fibers sold under the trade names of NOMEX(copyright) and KEVLAR(copyright). NOMEX(copyright) materials were developed for applications requiring dimensional stability and excellent heat resistance, and which do not flow or melt upon heating. Decomposition and charring does not proceed at a significant rate until well over 350xc2x0 C. without melting. NOMEX(copyright) materials in fibrous form have been used in protective apparel and similar applications, and can be processed by conventional textile technology. Heretofore, comparable flame-retardant nonwoven fabrics have been expensive to manufacture, and have not been susceptible of imaging by high pressure water jet entangling. Specific examples of prior art materials are set forth below.
U.S. Pat. No. 4,199,642 discloses a flame resistant fiberfill batt consisting of polyester fiberfill and synthetic organic filamentary materials, including poly(m-phenylene isophthalamide) blended therewith that maintains its physical integrity when exposed to the flame from a burning match.
U.S. Pat. No. 4,463,465 discloses an aircraft seat cushion including a highly heat-sensitive urethane foam covered by a flexible matrix, which may comprise a NOMEX(copyright) fabric. A further gas barrier layer may also be provided, which can also be a NOMEX(copyright) fabric.
A wet-type survival suit is disclosed in U.S. Pat. No. 4,547,904, including inner and outer NOMEX(copyright) layers, which provide maximum protection against fire.
A fire-retardant panel is disclosed in U.S. Pat. No. 4,726,987 and No. 4,780,359 which includes one or more layers of NOMEX(copyright) fiber that may be combined with adjacent fibrous layers by needle punching.
U.S. Pat. No. 4,748,065 discloses a flame resistant fabric, wherein a spunlaced fabric formed of fibers, such as NOMEX(copyright), is brush-coated with an aqueous slurry containing activated carbon particles. The resulting fabric was subsequently dried and softened by crepeing. Laminates, including spunlaced outer layers of NOMEX(copyright) fibers, are also disclosed.
A fire-blocking textile fabric is disclosed in U.S. Pat. No. 4,750,443, which includes three to seven nonwoven layers that are hydraulically needled to one another. Each layer may be formed of NOMEX(copyright) fibers; however, an outer woven layer may be provided to impart dimensional stability and abrasion resistance.
U.S. Pat. No. 4,937,136 discloses a laminate for use in fire protective garments. The laminate includes a nonwoven fabric comprised of a blend of wool and synthetic fibers capable of high temperature performance, such as NOMEX(copyright). The laminate includes an outer shell, which may also be formed of NOMEX(copyright) and an intermediate moisture barrier layer.
An animal bed cover is disclosed in U.S. Pat. No. 5,226,384, which is formed of an aramid fabric sheet, e.g. KEVLAR(copyright) with a polyester fabric sheet laminated to it.
In U.S. Pat. No. 5,252,386, a fire retardant entangled polyester nonwoven fabric is disclosed. The patent states that the fabric has balanced tensile strength properties in the cross- and machine-directions and improved fire retardant properties by cross-stretching the entangled fabric, after the fabric has been wetted with an aqueous-based fire retardant composition, and drying the wetted fabric while maintaining it in its stretched state.
U.S. Pat. No. 5,279,879 discloses a flame-retarding nonwoven fabric formed of partially graphitized polyacrylonitrile fibers that are bonded by water jet needling. The fabric may be reinforced by warp-wise and weft-wise threads, and the fabric may be combined with a decorative fabric/material by adhesive securement.
U.S. Pat. No. 5,475,903 discloses a fabric that is formed by carding synthetic fibers, such as polyester fibers, cross-lapping the carded web to orient the fibers in the cross-direction, drafting the cross-lapped web to reorient certain of the fibers in the machine-direction, applying unbonded wood fibers to the top of the drafted web, and hydroentangling the resulting web to entangle the wood fibers with those of the polyester drafted web. A liquid fire-retardant composition is then applied to the hydroentangled web.
In U.S. Pat. No. 5,578,368, a fire-resistant material is disclosed, which includes a fiberfill batt, that may comprise polyester fibers, and a fire-resistant aramid fibrous layer like NOMEX(copyright), at one, or both, faces of the batt. The aramid fiber layer may be joined to the fiberfill batt by hydroentangling.
U.S. Pat. No. 5,609,950 and No. 5,766,746 disclose a flame-retardant nonwoven fabric wherein fleece, including cellulose fibers having a flame-retardant containing phosphorus, is bonded by water jet entanglement.
In order to provide adequate protection to the skin from burn damage by heat and/or flame, currently available fabrics for flame retardant clothing rely upon high basis weights and bulks. A practical consequence of extended wear of articles made of these heavy fabrics is fatigue and potential dehydration due to poor air circulation. Blends of melamine fibers (BASF Corporation under the trade name of BASOFIL) with varying ratios of aramid fibers, as is disclosed in U.S. Pat. No. 5,560,990, hereby incorporated by reference, are known. It has been discovered that when a melamine/aramid fiber blend is hydroentangled and a 3-dimensional image imparted, thermal protection to the skin at lower basis weights are maximized, thereby providing significantly improved wearer comfort and safety.
The fabric of the present invention is a hydroentangled, imaged nonwoven fabric formed from a blend of melamine and aramid fibers. While the heat and flame-resistant properties of aramid fibers are well understood and appreciated, fabrics produced using these aramid fibers are known to be heavy in weight and low in air permeability. When converted into flame retardant apparel, fatigue due to heat and dehydration in instances of extended wear, are commonplace.
It has been discovered that the use of melamine fibers, when blended with aramid fibers in relative ratios of between 45 weight percent and 55 weight percent, and preferably about 50 weight percent, of the melamine fiber, provides improvement in Thermal Protective Properties (TPP). In a preferred embodiment, a carded staple fiber blend is hydroentangled by the use of high-pressure water jets followed by imaging on a three-dimensional surface to provide a fabric with a basis weight range of between 65 grams per square meter and 150 grams per square meter, a resultant air permeability greater than 65 CFM per gram fabric weight per cubic centimeter and a TPP rating greater than 11.4 cal-sec per square centimeter.